Georgetown University – Washington, D.C.
The Dahlgren Chapel was built around 1893. The original construction consists of brick and stone masonry bearing walls above grade and stone block foundation walls below grade. The roof structure is framed with exposed wood trusses that incorporate steel ‘tension” tie rods at the base for thrust resistance.
Prior to our work, the historic chapel experienced significant foundation settlement that caused severe exterior wall cracking, major interior plaster separation, and cast-stone window mullion joint separation, which lead to some distressing and breaking of the original stained glass windows. Holbert Apple Associates performed a detailed damage survey and worked with a geotechnical consultant to establish the cause of the settlement, which was determined to be softening of soils due to broken water and storm lines located under the building.
Next Holbert Apple Associates prepared construction documents for an underpinning system to lower approximately 60% of the perimeter foundations to a layer of adequate soil bearing, as recommended by the geotechnical engineer. In addition, repairs were detailed to address the damaged masonry bearing walls.